1. Field of the Invention
This system relates to a camera system and a photometry circuit in an electronic flash device.
2. Related Background Art
A photometry circuit such as auto flash control in an electronic flash device has heretofore been designed such that an integration capacitor is charged with the photocurrent of a light receiving element directly or through an amplifier and the voltage thereof is compared with a reference value corresponding to a proper quantity of light by an analog comparator and on the basis of the result of the comparison, light emission is stopped and auto flash control is effected with the proper quantity of light.
In the prior art, the extent to which analog circuits such as a photocurrent integrating circuit, a comparator and reference voltage occupy space has been great and the interface when control is effected by a digital circuit such as a microcomputer has been difficult. In the prior art, the gain of an amplifier and a reference voltage at the most have been produced by a D/A converter and the control of the most of auto flash control has only been effected by an analog circuit. Accordingly, as compared with an electronic flash device before a microcomputer is carried therein, the circuit scale of the analog system has not become small and rather, the circuit has become complicated as the whole electronic flash device correspondingly to the fact that a microcomputer is carried therein, and this has led to the bulkiness and increased costs of the device.